Overcrowding in hospital emergency departments is a world-wide crisis resulting in long wait times and detriments to patient safety. Tissue oxygen saturation (StO2) is sometimes an early indicator of perfusion status in patients experiencing undifferentiated shock in emergency room triage settings. By indicating the need for, and allowing the start of, fluid and antibiotic therapy, monitoring StO2 in an emergency room triage setting can help identify high-risk patients in need of immediate attention and focus scarce emergency room resources on the most critical patients. High-risk patients who receive immediate StO2 monitoring in an emergency room setting have been shown to receive effective interventions sooner, resulting in significant reductions in ICU admission, length of stay, morbidity, and mortality.
Near infrared (NIR) spectrometer systems for measuring tissue oxygen saturation (StO2) are known and disclosed in, for example, U.S. Pat. No. 7,947,054 to Benni and U.S. Pat. No. 6,377,840 to Gritsenko et al., each of which are incorporated herein by reference in their entirety for all purposes.
The Benni patent discloses a spectrometer utilizing four laser diodes to provide discreet measurement radiation within the 700 nm to 1000 nm wavelength range. The use of laser diodes as the radiation source requires relatively complicated power controls and safety interlock controls. Coupled to each laser diode is a multimode optical fiber having a core diameter of 200 μm. A dual ball lens optical coupler assembly couples the fibers from each laser diode to a single multimode fiber having a core diameter of 300 μm, which connects to the patient interface. The patient interface is designed to be reused multiple times and includes a prism assembly to direct measurement radiation to the patient's measurement site and an EMI shielded photodiode assembly for receiving reflected radiation from the measurement site. A shielded electrical cable interconnects the photodiode assembly to the spectrometer's system processor. Frequent handling, detachment and reattachment of the patient interface subjects the single multimode 300 μm diameter fiber to multiple bending stresses, which can lead to premature failure of the fiber. Additionally, manufacturing the patient interface is made more complex and is thus more costly since the prism and EMI shielded photodiode assemblies are incorporated into the patient interface.
The Gritsenko et al. patent discloses a spectrometer utilizing four LED's to provide discreet measurement radiation at wavelengths of 680 nm, 720 nm, 760 nm and 800 nm, respectively. The spectrometer includes an electronics package, an optical probe for interfacing with the patient measurement site, and a probe connector for coupling the optical probe to the electronics package. The electronics package includes a processor/controller and a relatively complex optical bench for detecting and processing radiation that has been reflected from the measurement site. The optical probe connector includes the measurement source and reference LED's, an electrical connector for connecting the LED's to the electronics package, optical fibers for transmitting measurement and reflected radiation to and from the optical probe, and optical connector ferrules for connecting reference and reflected radiation to the optical bench. The optical bench comprises a series of mirrors, band pass filters, and photomultiplier tube sensors. In operation, measurement radiation from the 680 nm, 720 nm, 760 nm, and 800 nm LED's is transmitted simultaneously to the tissue within the measurement site. Radiation reflected from the measurement site is transmitted to the optical bench via the optical probe connector where it is separated into discreet wavelength components. The optical probe that interfaces with the patient measurement site is connected to the optical probe connector by an optical fiber bundle comprising a single fiber for each of the measurement radiation LED's and a single fiber for transmitting reflected radiation.
There remains a need for a portable, hand-held spectrometer for quickly and efficiently measuring tissue oxygenation. To be commercially viable, any such spectrometer must be easy to use, easy to maintain, and cost effective to manufacture.